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Understanding Alzheimer's Disease -- the Basics

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What Is Alzheimer's Disease?

Alzheimer's disease or Alzheimer's-type dementia is a progressive degeneration of brain tissue that primarily strikes people over age 65. It is the most common cause of dementia and is marked by a devastating mental decline. Intellectual functions such as memory, comprehension, and speech deteriorate.

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Understanding Alzheimer's Disease

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Memory impairment is an essential feature of Alzheimer’s disease and is often the first sign. Recent memory is lost first. As time goes on, attention tends to stray, simple calculations become impossible, and ordinary daily activities grow increasingly difficult, accompanied by bewilderment and frustration. These symptoms tend to worsen at night. Dramatic mood swings occur -- outbursts of anger, bouts of fearfulness, and periods of deep apathy. The sufferer, increasingly disoriented, may wander off and become lost. Physical problems, such as an odd gait or a loss of coordination, gradually develop. Eventually, the patient may become physically helpless, incontinent, and unable to communicate entirely.

Alzheimer's disease can run its course from onset to death in just a few years, or it may play out over a period of as long as 20 years. More often, however, people suffer with Alzheimer's disease for about nine years. It is the sixth leading cause of death in the U.S. One person out of eight age 65 and over has the disease. Women are more susceptible than men, and half of all nursing home residents suffer from Alzheimer's or related disorders.

What Causes Alzheimer's Disease?

Typically, people develop Alzheimer's disease as they grow older, but the disease is not a natural result of aging. It is an abnormal condition whose causes continue to be investigated.


The gradual loss of brain function that characterizes Alzheimer's disease seems to be due to two main forms of nerve damage:

  • Nerve cells develop tangles (neurofibrillary tangles)
  • Protein deposits known as beta-amyloid plaques build up in the brain (Figure 2)

Researchers are not yet sure why or how these processes occur, but some of the most promising recent research points to a normally occurring blood protein called ApoE (for apolipoprotein E), which is required for the transport of fatty substances in the body.

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